passenger

right now I'm in the middle of setting up new payplay server with completely new configuration.

For a long-long time PayPlay.FM was running under lighty + fcgi/mongrel_cluster.
It worked but had a lot of problems starting with lighty's poor mod_proxy (resulting in 100% CPU load just because it can't re-enable crushed proxy) and ending with huge memory eating. We had like 5 mongrels, 200 Mb each. Awful. If you add 1G for memcached, and 700Mb for mysqld, you'll find that you've got not so much memory as you expected.

So here is what I change now:

1. enterprise ruby authors claim it has 33% memory benefit which is great.
2. passenger aka mod_rails

Some notes for future:

1. if you can't see your assets (css,images, 403 forbidden) - just add "allow from all" to the end of your VirtualHost's Directory section.
2. remember that passenger will run under user that is owner of config/environment.rb (+ one root spawner)